When using mobile packet switched services there is in some cases a need to use an Internet Protocol (IP) point of presence (POP) that is, in the network topology, located closer to the physical location of the user equipment. This need may arise due to several reasons.
One such reason could be to avoid suboptimal routing that would occur if the user equipment (UE) (also referred to as a mobile terminal) keeps its IP point of presence and uses the same IP address to communicate, while it moves far away from the IP point of presence. This may cause inefficiencies depending on what kind of services the UE is using. The inefficiencies could arise in the form of too long delays, too low throughput (e.g., due to the long delay when Transport Control Protocol (TCP) is used as the transport protocol). Additionally, the suboptimal routing can cause unnecessary transmission costs for the operator.
Another reason for the need of a local IP point of presence is to use localized content, where the localization could be based on the IP address. Another example of this is local multicast services.
In addition, IP mobility solutions, namely Mobile IP (RFC 3344, IP Mobility Support for IPv4; RFC3775, Mobility Support in IPv6), may require a local IP address to work in the mobile system. Note that Mobile IP based solutions are being discussed for the new System Architecture Evolution (SAE) system architecture (3GPP TR 23.882, System Architecture Evolution Report on Technical Options and Conclusions), though there is no conclusion yet if they will eventually be used.
In the current General Packet Radio Service (GPRS), mobile terminals can request a new IP address using the packet data protocol (PDP) context activation procedure. This procedure is initiated by the terminal, and it is typically invoked when the terminal expects to use packet switched services. There is no mechanism in GPRS where terminal mobility would trigger the activation of a new PDP context. Also, there is no easily deployable mechanism for a network-initiated IP address allocation. In other words, there is no network-initiated PDP context activation procedure. For these reasons, current GPRS technology does not provide the means to satisfy the need for a local IP point of presence.
Note that one exception exists: when the mobile terminal roams to a new network, it may perform a new attach and subsequently a new PDP context activation procedure which can allocate a local IP point of presence (i.e., local IP address) in the visited network. This typically occurs when the mobile terminal moves to a new network operator. But according to the discussion above, there is also a need to allocate a local IP point of presence, which is initiated by the network, even when the mobile terminal remains in the same network. This need is especially high in networks that span over a large geographical area, e.g. USA or China.
Although Mobile Internet Protocol version 6 (MIPv6) route optimization could be used to solve the routing optimization problems, it has a number of disadvantages. First, the policy enforcement point is changed in an ongoing flow which may compromise charging and policy control enforcement. Second, policy and charging enforcement becomes more complicated because the network has to process more headers, i.e. those associated with Mobile IP. Third, moving the enforcement point could also require that the Policy Control and Charging Rules Function (PCRF) node is moved which introduces a lot of complexity, namely the transfer of context from the old to the new PCRF, and selection of the current PCRF becomes difficult.
Also note that MIPv6 would require that the terminal implements the corresponding MIPv6 protocol mechanisms which are assumed to be complex. Additionally, the correspondent nodes are also required to support MIPv6 route optimization. That means that the MIPv6 approach works only for IPv6 compatible networks.